Surface mounting package

ABSTRACT

A surface mounting package includes a metal base ( 1 ) with a lower surface having a through hole, a metal lead ( 2 ) arranged to be inserted into the through hole, an insulating material ( 3 ) filling in an internal space defined by the metal base ( 1 ), a cap ( 30 ) covering the metal base ( 1 ) as a lid, and an electronic part component arranged at a surface ( 2   i ) on the internal space side of the metal lead ( 2 ). The internal space is held at an air-tight atmosphere. The metal base ( 1 ) has a lower surface positioned on the same plane as a lower surface of the metal lead ( 2 ) or the insulating material ( 3 ), the same plane (P) forming a plane to be attached to a mounting board.

TECHNICAL FIELD

[0001] The present invention relates to a surface mounting package foran electronic part component, and in particular, to a structure in whicha metal lead is adhered to a metal base by an insulating material andexposed to the outside.

BACKGROUND ART

[0002] In a device such as a quartz resonator, a filter or anoscillator, as an electronic part for surface mounting, a surfacemounting package to be a housing contains an electronic part componentsuch as a piece of quartz, a piezoelectric device or the like. Examplesof such a surface mounting package typically include four types ofstructures each having a base and a cap, as will be described below withConventional Examples 1 to 4.

CONVENTIONAL EXAMPLE 1

[0003] A surface mounting package of Conventional Example 1 is formed,as shown in FIGS. 10 and 12, by first connecting a metal lead 6 forlead-out to a circular metal base 5 by a high-melting glass 7 which isan insulating adhesive (e.g. borosilicate), and then combining acylindrical cap 8 shown in FIG. 11 therewith such that an opening end 8e is coupled around metal base 5 for sealing. As can be seen from FIG.13, cylindrical cap 8 has legs 9 for holding its position, connected bywelding or the like to an outer periphery of the cylindrical portion.Cylindrical cap 8 in such a package is made of metal for preventingentry of external electromagnetic wave that interferes with the functionof a quartz resonator and the like.

CONVENTIONAL EXAMPLE 2

[0004] A surface mounting package of Conventional Example 2 is shown inFIG. 14. The package is formed by combining a box-shaped ceramic base 9with a platy ceramic cap 10 for covering a box opening 9 a. Only aninsulator is used as a material for the package. If there is no concernabout entry of electromagnetic wave, the package may be made of aninsulator alone as in Conventional Example 2, not using a metal materialas in Conventional Example 1.

CONVENTIONAL EXAMPLE 3

[0005] A surface mounting package of Conventional Example 3 is shown inFIG. 15. The package is formed by combining ceramic base 9 and atranslucent glass cap 11 that serves as a top plate to cover a ceramicbase opening 9 a, and sealing the package with low-melting glass 31. Thepackage uses a glass cap, so that oscillation frequency after sealingcan easily be adjusted by laser trimming.

CONVENTIONAL EXAMPLE 4

[0006] A surface mounting package of Conventional Example 4 is shown inFIG. 16. The package is formed by combining ceramic base 9 with a metalcap 12. A metal thin film 14 (e.g. silver brazing filler metal) isformed on an upper surface at the opening side of a spacer 13 formingsidewalls of ceramic base 9. Metal thin film 14 and metal cap 12 areconnected together by seam welding or electron-beam welding.

[0007] The surface mounting package according to Conventional Example 1,however, needs to ensure insulation between metal lead 6 and metal base5 by providing an insulating material around metal lead 6, whichincreases the outer diameter of the package by a distance required forinsulation, and thus adversely affects thinning of the package. As forother conventional techniques, each of the surface mounting packagesaccording to Conventional Examples 2 to 4 has a limit on thinning of thepackage, since it is difficult to reduce a bottom-plate thickness 15 ofthe base due to constraints in the composition and characteristics ofceramic base 9 used as a base material. Excessive reduction in thedimension would adversely affect the air tightness, moisture resistanceand strength of the package.

DISCLOSURE OF THE INVENTION

[0008] In view of the conventional circumstances as described above, anobject of the present invention is to provide a surface mounting packagethat allows further reduction in the thickness.

[0009] To achieve the object, a surface mounting package according tothe present invention employs a metal base in place of the combinationof an insulating ceramic base and a cap. A metal lead for lead-out isprovided at the bottom of the metal base having a surface to be attachedto a mounting board. The metal lead is configured to have a lowersurface coplanar with a lower surface of the metal base. By using metalas a base material, the bottom portion of the base, which had to be madethick to a certain degree when a ceramic base was used, can be madethinner. Moreover, the strength of the package can also be secured.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a plan view of a thin metal package as a surfacemounting package in the first embodiment of the present invention;

[0011]FIG. 2 is a section view taken along line II-II in FIG. 1 in thedirection of the arrow;

[0012]FIG. 3 is a section view taken along line III-III in FIG. 1 in thedirection of the arrow;

[0013]FIG. 4 is a plan view of a thin metal package as a surfacemounting package in the second embodiment of the present invention;

[0014]FIG. 5 is a section view taken along line V-V in FIG. 4 in thedirection of the arrow;

[0015]FIG. 6 is a section view taken along line VI-VI in FIG. 4 in thedirection of the arrow;

[0016]FIG. 7 is a plan view of a thin metal package as a surfacemounting package in the third embodiment of the present invention;

[0017]FIG. 8 is a section view taken along line VIII-VIII in FIG. 7 inthe direction of the arrow;

[0018]FIG. 9 is a section view taken along line IX-IX in FIG. 7 in thedirection of the arrow;

[0019]FIG. 10 is a section view showing the metal package inConventional Example 1 of the surface mounting package;

[0020]FIG. 11 is a section view taken along the direction of axis of acylindrical cap for the metal package in Conventional Example 1 of thesurface mounting package;

[0021]FIG. 12 is a section view taken along line XII-XII in FIG. 10 inthe direction of the arrow;

[0022]FIG. 13 is a section view taken along line XII-XIII in FIG. 11 inthe direction of the arrow;

[0023]FIG. 14 is a section view of the ceramic package in ConventionalExample 2 of the surface mounting package;

[0024]FIG. 15 is a section view of the ceramic package in ConventionalExample 3 of the surface mounting package; and

[0025]FIG. 16 is a section view showing the package in ConventionalExample 4 formed by combining a metal cap with a ceramic base.

BEST MODES FOR CARRYING OUT THE INVENTION

[0026] The present invention will clearly be understood by the followingdescription of embodiments.

[0027] First Embodiment

[0028] The first embodiment of a surface mounting package for a quartzresonator according to the present invention will be described withreference to FIG. 1. In the present embodiment, the surface mountingpackage includes an assembled base 4 in which a metal base 1 and a metallead 2 are adhered together by an insulating material 3, and a metal cap30 illustrated by a chain double-dashed line. Metal base 1 constitutingassembled base 4 forms a metal cavity structure (i.e. a structure inwhich a part of a metal box is cut out) as shown in FIG. 1, and has abase bottom portion 16 provided with a through hole 160. Metal lead 2 isof a quadrangular prism with an inner surface 2 i and an outer surface 2o of the six surfaces serving as an inner electrode and an outerelectrode, respectively. Metal lead 2 is shaped to be accommodated tometal base 1 and is inserted into a position corresponding to throughhole 160. The size and shape of through hole 160 in metal base 1correspond to those of metal lead 2. It is noted that FIGS. 2 and 3 aresection views taken along lines II-II and III-III, respectively, in FIG.1 in the direction of the arrows.

[0029] A surface 2 o which is to be the lower surface of metal lead 2and the lower surface of base bottom portion 16 form a plane P used whenthe package is attached to a mounting board. Plane P may be flat when itis fixed by blazing to a flat printed board or the like, but is formedto be a curved plane when it is attached to a cylindrical surface, toconform thereto.

[0030] Further, a gap space generated when metal lead 2 is inserted intometal base 1 is filled with e.g. borosilicate glass, which ishigh-melting glass, as an insulating material 3. Heat is applied to weldthe insulating material, to adhere metal lead 2 to metal base 1. It isunderstood that Ag-based glass which is low-melting glass may be used asinsulating material 3 for an electronic part component susceptible tohigh-temperature adhesion.

[0031] A quartz piece is fixed to a pair of lead electrodes 2 onassembled base 4 configured as described above. Metal base 1 is coveredand coupled with a metal cap 30 indicated by chain double-dashed linesin FIGS. 2 and 3. In order to allow adjustment of oscillation frequencyby applying ultraviolet light to an electronic part component after asurface mounting package is completed, borosilicate glass may be used inplace of metal cap 30, in consideration of translucency.

[0032] Second Embodiment

[0033] The second embodiment of a surface mounting package for a quartzresonator according to the present invention will be described withreference to FIG. 4. The surface mounting package includes assembledbase 4 in which metal base 1 and metal lead 2 are adhered together byinsulating material 3, and a metal cap (not shown). Metal base 1constituting assembled base 4 forms a metal cavity structure (i.e. astructure in which a part of a metal box is cut out) as shown in FIG. 1,and has base bottom portion 16 provided with two through holes 161, 162as shown in FIG. 5. Metal lead 2 is of a quadrangular prism, two of thesix surfaces serving as an inner electrode and an outer electrode. Metallead 2 is shaped to be accommodated to metal base 1 and inserted into aposition corresponding to each of through holes 161, 162. The size andshape of each through hole 161, 162 in metal base 1 correspond to thoseof metal lead 2. It is noted that FIGS. 5 and 6 are section views takenalong lines V-V and VI-VI, respectively, in FIG. 4 in the direction ofthe arrows.

[0034] Further, a gap space generated when metal lead 2 is inserted intometal base 1 is filled with insulating material 3 of high-melting glass.Heat is applied to weld the insulating material, to adhere metal lead 2to metal base 1. Here, insulating material 3 may not necessarily be madeof a glass-based material. For instance, polyimide-based resin and thelike may also be used when the glass-based material is unacceptable dueto the specification of an electronic part component.

[0035] As an electronic part component, for example, a piezoelectricdevice is fixed to a pair of lead electrodes 2 on assembled base 4configured as described above. Metal base 1 is covered and coupled withmetal cap 30 (not shown). It is noted that an oscillator including afilter and a semiconductor device may also be employed as an electronicpart component. Metal lead 2 is not limited to a bar-shaped one with arectangular section, but may have an approximately circular shape whenthe electronic part component uses small power and employs low currentrating. Moreover, if a surface mounting package completely-shielded fromelectromagnetic wave is desired, metal cap 30 may be formed, forexample, of an Fe—Co—Ni alloy.

[0036] Third Embodiment

[0037] The third embodiment of a surface mounting package for a quartzresonator according to the present invention will be described withreference to FIG. 7. The surface mounting package includes assembledbase 4 in which metal base 1 and metal lead 2 are adhered together byinsulating material 3, and a metal cap (not shown). Metal base 1constituting assembled base 4 forms a metal cavity structure (i.e. astructure in which a part of a metal box is cut out) as shown in FIG. 1,and has a base bottom portion 16 provided with one through hole 160.Metal lead 2 is of a quadrangular-prism-like shape having a curvedsurface, two of the six surfaces serving as an inner electrode and anouter electrode. Metal lead 2 is shaped to be accommodated to metal base1 and inserted into a position corresponding to through hole 160. Thesize and shape of through hole 160 in metal base 1 correspond to thoseof metal lead 2. It is noted that FIGS. 8 and 9 are section views takenalong lines VIII-VIII and IX-IX in FIG. 7, respectively, in thedirection of the arrows.

[0038] Further, a gap space generated when metal lead 2 is inserted intometal base 1 is filled with borosilicate glass, which is high-meltingglass, as insulating material 3. Heat is applied to weld the insulatingmaterial, to adhere metal lead 2 to metal base 1.

[0039] A piezoelectric device is fixed to a pair of lead electrodes 2 onassembled base 4 configured as described above. Metal base 1 is coveredand coupled with a metal cap (not shown). Here, for example, Ag-basedglass may also be used as insulating material 3 when an electronic partcomponent desires no high-melting glass as an insulating material.

[0040] While the lower surface of metal lead 2 was coplanar with that ofmetal base 1 in the embodiments above, the lower surface of insulatingmaterial 3, instead of metal lead 2, may have the same plane as thelower surface of metal base 1. Alternatively, as illustrated, the lowersurfaces of metal lead 2, insulating material 3 and metal base 1 may allbe on the same plane.

[0041] As can be understood from the description above, the surfacemounting package according to the present invention eliminates the needfor providing an insulating material around a metal lead an in aconventional package (Conventional Example 1), allowing the package tobe made thinner and smaller. By changing a base material from ceramic tometal, the air tightness, moisture resistance and strength of thepackage can be secured even if the base bottom plate portion has a smallthickness.

INDUSTRIAL APPLICABILITY

[0042] The present invention may be applicable to a surface mountingpackage used in surface mounting of an electronic part component such asa quartz resonator, a filter, an oscillator and the like, and is usefulin further thinning of the surface mounting package.

1. A surface mounting package, comprising: a metal base (1) with a lowersurface having a through hole; a metal lead (2) arranged in said throughhole; an insulating material (3) filling in an internal space defined bysaid metal base (1); a cap covering said metal base (1) as a lid; and anelectronic part component arranged at a surface (2 i) on said internalspace side of said metal lead (2), said internal space being held at anair-tight atmosphere, said metal base (1) having a lower surfacepositioned on a same plane as a lower surface of said metal lead (2),said same plane (P) forming a plane to be attached to a mounting board.2. The surface mounting package according to claim 1, wherein said planeto be attached is a flat plane.
 3. The surface mounting packageaccording to claim 1, wherein said plane to be attached is a curvedplane.
 4. The surface mounting package according to claim 1, whereinsaid electronic part component is adhered by a high-melting solder. 5.The surface mounting package according to claim 1, wherein said metallead (2) is a bar with a rectangular section.
 6. The surface mountingpackage according to claim 1, wherein said metal lead (2) is a bar withan approximately circular section.
 7. The surface mounting packageaccording to claim 1, wherein said insulating material (3) ishigh-melting glass.
 8. The surface mounting package according to claim1, wherein said insulating material (3) is low-melting glass.
 9. Thesurface mounting package according to claim 1, wherein said insulatingmaterial (3) is a polyimide-based resin material.
 10. The surfacemounting package according to claim 1, wherein said cap is made of ametal Fe—Ni—Co alloy.
 11. The surface mounting package according toclaim 1, wherein said cap is borosilicate glass.
 12. A surface mountingpackage, comprising: a metal base (1) with a lower surface having athrough hole; a metal lead (2) arranged to be inserted into said throughhole; an insulating material (3) filling in an internal space defined bysaid metal base (1); a cap covering said metal base (1) as a lid; and anelectronic part component arranged at a surface (2 i) on said internalspace side of said metal lead (2); said internal space being held at anair-tight atmosphere, said metal base (1) having a lower surfacepositioned on a same plane as a lower surface of said insulatingmaterial (3), said same plane (P) forming a plane to be attached to amounting board.